Our research goals for the coming year include: 1) kinetic studies of the beta-aminoethyl phosphate diesters in order to establish the requisite Bronsted relationships for delineating the transition state in the phosphoryl transfer process; 2) rapid stopped-flow kinetic studies on FBPase to determine a) the number of active sites involved in turnover b) the possibility of a rapid transient phase preceding the steady-state turnover and c) proton release upon substrate binding; 3) modification of the active-site tyrosine residues in FBPase based on our earlier preliminary findings that four of these residues rapidly react with tetranitromethane; and 4) the continuation of our stereochemical studies involving chiral phosphorothioate substrates and phosphodiesterases, having found that one enantiomer of phenyl p-nitrophenylphosphorothioate reacts with the snake venom and bovine intestine enzymes. Under 4) we will now focus our effort on obtaining the absolute stereochemistry of our reactive enantiomer as well as the reaction stereo-chemistry of the hydrolysis process.